Deciphering Mechanisms of Respiratory Foetal-to-Neonatal Transition in Very Preterm Infants

The respiratory mechanisms of a successful transition of preterm infants after birth are largely unknown.To describe intrapulmonary gas flows during different breathing patterns directly after birth Methods: Analysis of electrical impedance tomography (EIT) data from a previous randomized trial in preterm infants 26-32 weeks gestational age. EIT data for individual breaths were extracted and lung volumes as well as ventilation distribution were calculated for end of inspiration, end of expiratory braking/holding manoeuvre and end of expiration.Overall, 10'348 breaths in 33 infants were analysed. We identified three distinct breath types within the first ten minutes after birth: tidal breathing (44% of all breaths; sinusoidal breathing without expiratory disruption), braking (50%; expiratory brake with a short duration) and holding (6%; expiratory brake with a long duration). Only after holding breaths, end-expiratory lung volume increased [median (IQR) 2.0 (0.6 to 4.3) AU/kg vs 0.0 (-1.0 to 1.1) vs 0.0 (-1.1 to 0.4), p<0.001]. This was mediated by intrathoracic air redistribution to the left and non-gravity-dependent parts of the lung via pendelluft gas flows during braking/holding manoeuvres.Respiratory transition in preterm infants is characterized by unique breathing patterns. Holding breaths contribute to early lung aeration after birth in preterm infants. This is facilitated by air redistribution during braking/holding manoeuvres via pendelluft flow which may prevent lung liquid reflux in this highly adaptive situation. This study deciphers mechanisms for a successful foetal-to-neonatal transition and increases our pathophysiological understanding of this unique moment in life.